Carolyn Feasts on Muffaletta (featuring more Katana!)

Like my Joe Diamond deck (https://arkhamdb.com/deck/view/3617338), this is a true solo deck that features Katana. In this version, Carolyn Fern doubles down on the Steady-Handed mechanic by including Lab Coat, Chemistry Set, and most notably Olive McBride (thus the muffaletta reference).

The Basic Idea

Carolyn can run card combinations no one else can so she's always worth considering as a home for cards that seem to miss the mark in other investigators. Katana and Chemistry Set reward you for hitting specific numbers. Olive McBride gives you a range of test outcomes to choose from. Lab Coat and Steady-Handed let you play around with Olive's options to hit a targeted result.

Mulligan and Set-up

Especially at only 3xp, you're hoping for a bit of luck. (You're starting with singletons of some important 1xp cards.) You're digging for Katana and Olive McBride. Captivating Discovery is a decent consolation prize. Using Chemistry Set without Lab Coat is a bit risky so I might mulligan that even though it can help with setup.

Combat

Admittedly, Carolyn needs a lot of help to reliably succeed by 2 on the Katana. Wolf Mask, Reliable, and a suite of skill cards get her in the ballpark and then Olive, etc. help you reach exactly +2. Note that the Wolf Mask could also help her with the follow-up attack action on Katana.

Investigation

Chemistry Set plays nicely with Carolyn's high intellect. Lab Coat is at worst cheap insurance against loosing the Chemistry Set but is more often effectively a +1 intellect that nets a clue and two resources. Essentially all the skill cards can help at higher-shroud locations.

Economy and Card Draw

Chemistry Set and Carolyn's signature ability should provide enough income for this relatively low-cost deck. Chemistry Set, Hypnotic Therapy, and the core set skill cards give you reasonable draw. Captivating Discovery is slow but feels less bad if you can snag both a Deduction and a key asset from it.

Surviving

You have sanity soak and healing covered, even if you start at -2 sanity due to In the Thick of It. Save Deny Existence for big health hits. Medical Student can save you in a pinch. Don't overlook Lab Coat's 1/1 in the late game if you're done gathering clues. Inspiring Presence can give Olive McBride a bit more health soak and allow you to take a second bite at the apple if you whiff on a Katana swing. Wolf Mask gets you to 4 agility (not great but can take some of the edge off Grasping Hands and similar fail-by treacheries).

Action Economy

This is a slow deck. It takes a lot of setup and has zero movement tech. However, the Katana can eliminate enemies faster than any other level-zero weapon and the Chemistry Set should eliminate the need for Draw and Resource actions.

Other Cards of Note

Tinker would let you play a second Chemistry Set or free up your accessory slot for Hallowed Mirror, etc.

You have a ton of wild symbols on your skill cards but you'll use at least one skill card on essentially every Katana test, so don't fret too much about boosting close willpower tests as you can soak and heal a ton of sanity.

If Rational Thought pops up mid-game or later, you might be okay letting it ride.

Level Zero Options

Prepared for the Worst is in-class and might be a prudent addition. Backpack could also save the day but there's a good chance it will whiff with so few items.

If 3 willpower worries you, the Cat Mask might be a better (albeit out-of-class) option. It would probably refill itself reliably enough in scenarios or campaigns with lots of cultists or other doom acceleration.

Glory could replace Captivating Discovery to free up some out-of-class slots but I like the latter for helping me find Katana early on, and Carolyn probably needs to have Katana in play before she make use of Glory.

Early Upgrades to Consider

Duplicates of Steady-Handed and Reliable will be priorities. The latter could go on Chemistry Set if you already have one one Katana. Note that Steady-Handed heals horror so doesn't eat up an out-of-class slot.

A duplicate Lab Coat can't hurt but uses an out-of-class slot.

Upgraded Overpower will provide more card draw.

Upgraded Backpack makes more sense than the Level 0 but you'll feel pretty bad if you draw it late game.

Enchant Weapon would reduce your reliance on skill cards, and its downsides (exhausting it and taking up an arcane slot) are non-issues in that you are generally relying on one #katana activation per round.